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N. PETERS. PHOTO-LITHOGRAPNER. wAsmNGToN, D C

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JOHN H. MILLS, or BoSToN, MASSACHUS'ETTS.I Lemsmmuvo. sarsaddwd Mat/*4, lees.L

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The Schedule referred to these Letters atent and making part of the same.

a" t Wh@ thse treentsehazz omaif `Be it'known that I, JOHN H. MILLS, of Boston, in

the county of Suffolk, and State ofMassach usetts, have made an .invention of certain new and -useful improvements, hating-reference to Steam}ih igi nery; and.' do hereby declare the following to be-afull, clear, and ex- "act description thereof, due reference being had to the accompanying drawings, makingpart of this specifica.-

tion, and in whi,c h-" `Figure' 1 is a verticaland transverse section;

Figure 2, a vertical and longitudinal section; and

Figure 3, azhorizontal section of one .section Aof a cast-,iron steam-generator, embodying my improvei The invention, comprisingthe subject-matter of this patent, willfbefound toembraceyseveral points of `practicalu tili ty"'and value; its object being to pro- `duce a `,stearimgenerator, 'which .shallVv combine the `requisites of cheapness, simplicity, durability, and

eectiveness; u

This-invention consists in the` construction `and `errangement'- ofQthesteam and water-pipes composing connectionsarelavoided, and-liability tolacture at any i point-undue expansion and contraction of metal composing it is" obviated; the union of the diiferent portions or pipes of each independent section being made f up of easy` curves, rather than by right angles,`the` fyirhole being as yhereinafter explained; the construction whichobtains this advantagealso preventing deposit y, of sediment throughout itsfentire area.

` Another point ofunovelty in my invention consists in 4prolongingthewater-legs or pipes composingthe sides `of the section of a boiler into a homogeneous pipe, f `and extending it below, and so as to support the' lire whereby the grate-bars aref retained comparatively 'uninjured for a greatlength of time, and fuel economized; in addition towhich, more steamegenerating surface is `p'rodueed,.'and the capacity of the generator` lgreatly increased.- i i Y And this invention further consists in the grate for, supporting-thefuel of a-fre,\integral `with the prolongation of the water-legs before referred to; .extreme `cheapness of manufacture being thereby secured, and' other advantages gained, which will be dulyreferred to.` Still another novel feature in this invention will be seen in the devices' for joining the different sections at two points only, by. the employment of tubular rightA and left sciew-I'ilugs,V ashereinafter explained.

. In .the-drawings before mentioned as accompanying thisspeciication, `and which illustrates my invention,

Axdenotes one section of a cast-iron steam-generator,

thegeneral structurebeing composed of a'number of these `sections properly joined together in number varying with theamount of steam `to be produced.

. 'This section iscomposed of an outer enclosing-pipe B, whichcompletes' the Ientire outline of the section; the general fornil of this pipe B, being oblong, with semicircularor arched ends, as shown at c c.

, l Extending across and between the two upright portions or sides `of-"the pipe B,is a curved pipe D, such pipe being disposed, at about one-third the height of .such' pipe B; a fullchamber E, being thus created between the branch-pipe D, and the lower pine or grate-har C.-

The space intervening between the arched 4pipe D, andthe upper end of the outer circumscribing-pipe D,

is occupied by a series of upright pipes, F G I EI, dtc.;A

the central one, E, of which is a perpendicular exten-l v `sion of the arched pipe D, the upper extremities of the Aside-pipes G H, being joined tov and communicating with it, while'the lower extremities are mergedintoV the sides or legs of the outer pipe B. 11

, .The above-described arrangement'of pipesis cast in one homogeneous pieceof metal, and aggeneral communication effected throughout the entire series. i I would call .particular attention to the fact' thatthe points of junction of the different pipes are produced from curves of easy and gradual inclination. 1

The upper extremities of the circumscribingfpipe B' are formed upon each side with a stearm-circulating orifice I, its lower extremity or grate-bar being |provided in like manner with water-circulating apertures J J. In making upa steam-generatorof a series of sections, constituted as above described, they are to be` placed face to face Atogether in a perpendicularposition, with shallow intervening spaces,` and united by tubular plugs K K, such plugs having right vand leftscrews cut upon their extremities to screw into the orifices I J, of the annular pipe B; the central portion of the periphery of such Aplugs being square or polygonal, to

admit of the application of a wrench by which they are screwed into the said orifices.

Fig. 2, of the accompanying drawings, shows two sections of a generator united by means of the tubular plugs, which, while effecting a rapid .andv perfectlyv secure union of the sections, also admit of the passage' of steam and water, as the case may be, through their boxes; this union of the sections by means of the plugs, entirely preventing separation of the sections from contraction and expansion,`now common to generators, the sections of which are united `by bolts passing through the whole series.' y

In iig. 3, ofthe accompanying drawings,-I.have^rep `resented a novel mode of constructing the grate-bar of the furnace ofthe generator, which is accomplished by forminglupon -the upper surface of the lower boundary. or branch water-pipe of the -annular pipe B, aseries o f laterally-projecting points or studs a a, &c.", so.

arrangedthat when two'sections are united, as before explained, the interstoes created bysuch points shall admit ofthe passage of -a sucient quantity of Yair to maintain.` the combustion ofthe fuel.

.This arrangement of the branchwater-pipe C, and the grate-bar cast integral with it, lis prodnctiveof several advantages: first, the water contained within such'pipe preserves it and the grate-bar at acomparatively low temperature, .by this means greatly enhancing the .durability of such parts. The low temperature of the water-pipe and grate-bar, as explained, also prevents to a great extent the formation of slags and clinkers, which is now ofcommon occurrence. The heatradiating surface, and consequently the steam-producing capacity of the generator is greatly increased by the adoption of the branch water-pipe C, as much heat from the ire above it is utilized, which at present is in most cases lost.

Another advantage resulting from casting the gratebar homogeneous with the annular pipe B, is that a section oranumher of sections may be transportedwithout the loss and leakage now attendant upon the carriage of a comparatively large number of independent grate-bars The level at which water should stand in the generator above described, is shown at a a., in ng. l of the drawings.

it will be thus seen that the upper portion of the section becomesa superheating-steam reservoir; the interstices between the pipes, F, G, and H, forming in aggregate a large heatcirculating area, which, while obviating the necessity of a steam-drum independent of the generator, also allows me to produce a very dry steam.

One of the advantages of the construction and arrangement of the before-described generator, is that a free circulation is permitted throughout its entire interior area,-thus permitting pressure 0f steam to dislodge any sediment which would collect, were the union of the different pipes effected by right angles, the curved form of the lower water-bar also causing sediment to collect at one point from whence it is easily removed.

Owing to the curved outlines of the pipes composing the section, they will yield and accommodate themselves to the inevitable expansion and contraction of the metal, and render fracture at any point not liable.

l It may also be found advantageous under `some ,conditions to increase the depth of this water-pipe, and to dispose within the enclosure formed by it and the arched bar D, a series of ordinary independent gratc-` bars for supporting the fuel.

With regard also to the merits of cast sectional generators, so far as they relate to safety, steam-generating capacity, economy of fuel, Sac., I have not detailed upon such features, as they have already been treated in previous patents whose general operations and merits are analogous to my own.

Having thus described the nature, operation, and advantages of my present invention,

Vhat I claim as novel and original with myself', and desire to secure by Letters Patent of the United States, is as follows:

l. I claim as my improvement in the cast sectional` boiler, the construction of the sections whereby the lower arm or branch water-pipe of each section shall form the grate-bar. and contain water, substantially as before explained.

2. In a steamgenerator composed of cast multitubular sections, l claim the construction and arrangement of different pipes thereof', having gradual and easy curves, as liereinbefore set forth and explained.

3. I claim the construction of the sections of the steam-generator, whereby the union of a series of sections is effected at two points only, the upper' serving as the steam-circulating passage, and the lower one as the water-passage, substantially as explained.

4. I claim the arrangement, for effecting the union of two adjacent sections of the steam-generator, of tubular plugs, having right and left screws, substantially as before explained.

5; I claim the construction and arrangement of the fuel-chamber and furnace-grate, whereby the Waterlegs of the cuter pipe are prolonged, and the series of points, essentially as herein shown' and described.

' JOHN H. MILLS.

Witnesses:

EDMUND H. HEWINS, FRED. CURTIS. 

